The present invention is directed to stackers of the general type disclosed in Hoffswell U.S. Pat. No. Re. 26,004. The invention, in one of its forms, is an improvement upon the apparatus of the patent; while in another form it provides an alternative structure for performing the same function.
The patented stacker has proved to be one of the most efficient and reliable stackers yet devised for the stacking of signatures delivered from the outfeed of a high-speed rotary printing press and signature former. It is inexpensive, requires very little floor space, produces a stack of signatures from which lifts may readily be removed while the stacker continues to run, functions very efficiently with signatures on a wide variety of different kinds of paper and consisting of different numbers of pages, and is easily adjusted to stack signatures of various lengths and widths with equal facility.
The stacker of the patent, however, occasionally fails to form an entirely satisfactory stack of signatures printed on relatively lightweight stock, especially if they consist of only a small number of pages. The stacks are generally adequate, but sometimes are not as good as may be demanded in the highest quality of work because the signatures in a stack may not be sufficiently registered with one another from front to rear. Such problems may arise in stacking four to eight-page signatures printed on stock which is less than about 32 pounds, which tend to buckle from the force of the feedroll pushing on their projecting trailing end portions.
The problem has been more serious in recent years due to increasing use of lightweight stock to hold down printing costs.